From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical memorandum comparing the valve lift and valve springs of the E.A.C. engine with the Hawk and Falcon engines.
| Identifier | WestWitteringFiles\L\Jan1924-March1924\ Scan22 | |
| Date | 1st January 1924 | |
| TO R.{Sir Henry Royce} FROM E.{Mr Elliott - Chief Engineer} ORIGINAL SECRET E1/M18. 1. 24. Copy to - GJ. HS.{Lord Ernest Hives - Chair} HG. re. E.A.C. VALVE LIFT & VALVE SPRINGS. X9060 VALVE LIFT. The valve lift with which the EAC. engine is at present running is slightly less than pro rata Goshawk reckoned on the valve port diameter, but it is a little more than Hawk and Falcon, these latter being .46", and EAC. .49". The effective EAC. valve port opening however is less than Hawk and Falcon due to the use of 45º valve seats as against 30º as shewn below and we were balanced between getting the valve lift too high, and getting the power too low:- EAC. .0875 .49" .407" 45º HAWK & FALCON .075" .46" .42" 30º SCALE - 4/1 The effective EAC. port area between the valve head and the seat is just equal to the area of the 1.75 dia. port less the valve stem, and there-fore reckoning in the effect of the valve lift is none too large for the valve. The effect of the 45º could be partly countered by making the seatings nar-rower than we have hitherto used in car practice. The above are the considerations on which the EAC. valve lift was based. Nevertheless we afterwards suggested and received your assent to producing some lower lift cams and expect to calculate these next week. We propose to make these .4" lift which is the same as present 40/50. VALVE SPRINGS. The mean stress in the EAC. valve spring is identical with the mean stress in the largest convolution of the present 40/50 spring, but the stress range is 18% more. It was on this account that the lower lift was more desired. (1) | ||